Glass inspection apparatus



Sept. 3, 1940. E. L. WALTERs GLASS INSPECTION kAPPARATUS Filed Sept. 22, 1957 5 Sheets-Sheet 1 nnentor EMMa-Tr L. WALTER@ Gttomeg Sept. 3,` 1940. E. l.. wALTERs GLASS INSPECTION APPARATUS Filed Sept. 22, 1937 5 Sheets-Sheet 2 Snnentor EMMETT l.. wnLTE/ra G ttorneg Sept. 3, 1.940. E. 1.. wALTERs 2,213,422

GLASS INSPECTION APPARATUS Filed Sept. 22, 1937 5 Sheets-Sheet I5 rwentor EMMETT' l.. WALTER.

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Sept 3, 1940. E. l.. wAL'rr-:Rs 2,213,422

GLASS INSPECTION APPARATUS` 5 Sheets-Sheet 4 Filed sept, 22; 1937 Snventor EMMETT L. WALTE/as.

T' 1 1D- A l :2. U/ Gtvtorneg Sept 3, 1940. E. L. WALTERS` 2,213,422

GLASS INSPECTION APPARATUS` Filed Sept. 22, 1937 5 Sheets-Sheet 5 lnvcntor EMMETT L. WHL TEA.

Cttorncg Patented Sept. 3, 1940 .PATENT "OFFICE GLASS INSPECTION APPARATUS Emmett L. Walters, Toledo, Ohio, assigner to, Libbey-Owens-Ford Glass Company, Toledo, Ohio, a corporation of Ohio.

Application ySeptember 22, 1937, Serial No. 165,015

2 Claims.

The present invention relates to a'n apparatus for inspecting sheet glass and constitutes an irnprovement upon my Patent 2,046,045, issued Julie 3o, 1936. i

The inspection apparatus disclosed in said patl, ent embodies separate means Ifor forming twospaced bands of polarized light extending transf 15 unit and then the other in order to check the sheet across its entire width.

It is the object of this invention to provide a more compact and. eiiicient arrangement' for facilitating the inspection of the glass sheet 2o throughout its entire width simultaneously and by a single inspector. According to the invention', thetwo bands of polarized light which extend transversely of the'glass sheet are superimposed one upon the other rather than being 25 spaced apart as in my` earlier patent so that there is provided, in effect, but a single band of polarized light. -Also, instead of using' two analyzer units, only a single unit is, necessary, said unit comprising two analyzers, one being provided for 30 and set to analyze the light from each ofthe light polarizing means. Consequently, a Single inspector viewing the glass through the single analyzer unit will be able to inspect the sheet across its entire width without moving from' his position. 3 5 Such anrarrangement is not only more compact but permits a more rapid and efficient inspection of the glass sheet.

Other objects. and advantages of the invenltion will become more apparent during the course 40 of the' following description when taken in connection with the accompanying drawings.

In the drawings wherein like numerals are employed to designate-1v like parts throughout the Ysame:

Fig. 1 is a plan view illustrating diagrammatically.the two bands of polarized light superimposed upon one another and formed-by the light polarizing means provided by the invention;

Fig. 2 is a longitudinal sectional view taken 50 substantially on line 2-2 of Fig..1;

Fig. 3 4is a transverse sectional view/ showing Fsomewhat diagrammatically the light polarizing means for use inthe transverse inspection of the glass sheet; l 4 65 Fig. 4 is a diagrammatic plan view showing the (o1. ssa-,14) p arrangement of the light polarizing reflectors of Fig. 3;

Fig. 5 is a plan view showing in broken lines .the pattern of light formed upon the glass sheet when the polarizing reflectors are arranged as in Fig. 4;

Fig. 6 is a transverse sectional view'showing the arrangement of the light polarizing reflectors for obtaining the diagonal inspection of the glass sheet;

Fig..7 is a diagrammatic plan view of the light polarizing reflectors of Fig. 6;

Fig. 8 is a plan view showing in broken lines the pattern of light formed upon the glass when the polarizing reflectors are arranged as in Figs. 6 and '7;

Fig. 9 is a vertical longitudinal sectional view througha portion of the light polarizing means showing in enlarged detail one.of the polarizing units;

Fig. 10 is a perspective view o unit; j Fig. l1 is a sectional view of one of the analyzers taken substantially on line II--II of Fig.

the analyzer Fig. 14 isa diagrammaticl plan view. showing the'areas of the glass sheet covered by the diag--y onal inspection. Referring now to the drawings and particularly to Fig. 1, the numeral I 5 designates the outlet end of a horizontal annealing leer of any conventional or preferred construction and I6 a sheet or ribbon of glass emerging therefrom. 'I'he glass sheet, upon issuing from the leer, is received and carried forwardly upon a series of Y horizontally aligned rolls I1 journaled at their opposite ends in bearings I8 and I9 mounted upon fixed horizontal supports and 2lrespectively. The rolls I'I are spaced so as not to in any way interfere with the inspection apparatus and may be sitively driven from one end through sprockeI 'and' chain drive o r the like 22.. Y ll'he glass sheet I6; upon leaving the annealing per 15/1 for defects in a substantially continuous manner' as' it is/being/ carried forwardly. In order to eectl complete and thorough inspectionof the ferent angles'byl means of inspection apparatus so constructed and arranged as to cover the enf adaptedS torbe' inspected and marked is adapted to be inspected from two diftire area of the sheet transversely thereof and render visible all of the defects therein irrespective of the direction in which they might extend. More specifically, the sheet is caused to undergo a so-called diagonal inspection and also a transverse inspection, the transverse inspection covering certain spaced areas of the sheet transversely thereof and the diagonal inspection covering the remaining and complemental areas of said sheet transversely thereof, so that as a result a single inspector can readily observe defects extending in 'any direction across the glass.

vided with two analyzers, one being provided for andl set to analyze the light from each light polarizing means. Thus, one analyzer is arranged so as to cover spaced areas of the illuminated zone complementary to other spaced areas of said z one covered by the other analyzer, asV will be more fully hereinafter described.

As illustrated in Fig. l, the two bands of polarized light are indicated diagrammatically at A and.I B, both bands of light being arranged at an angle of 90 degrees with respect to the path of travel of the glass sheet and superimposed one upon the other. The vibrations of the band of polarized light A extend parallel to the glass travel while-the vibrations of the band of polarized light B extend substantially at an angle of forty-live degrees with respect to the glass travel.v The band of light A is formed by the light polarzing means utilized in making the transverse inspection and designated in its entirety by the letter C (Figs. 3 and 4) while the band of light B is created by the light polarizing means D (Figs. 6 and 7) employed for effecting the diagonal inspections As will be noted in Fig. 2, the light polarizing means C and D are both arranged beneath the glass sheet. The means for analyzing the polarized light comprises any analyzer unit E arranged above the sheet and to one side thereof,'said analyzer unit comprising two analyzers 23 and 24, one being provided for and set to analyze the polarized light from each light polarizing means C and D which create the bands of light A and B respectively.

As shown in Figs. 3 and,4, the light polarizing means C, forming the band of polarized light A, consists of a plurality of relatively small polarizing units 25, each comprising a source of illumination 26 and an inclined polarizing reflector 21. The polarizing surfaces of .the reflectors are arranged relative to one another in such a manner that the beams of polarized light from the center of each surface converge at a point above and to one side of the edge of the glass sheet being inspected. The analyzer unit E is adapted to be located at this apex or, in o-ther words, at the meeting line of the beams of polarized light. It will be noted that the angle of inclination of the polarizing reflectors 21 gradually decreases from the reflector a to the reflector b, the reflector a being arranged at substantially a sixty degree angle to the horizontal while reflector b is arranged at an angle of approximately ten degrees to the horizontal. However, the light ,sources are so arranged that the angle of reection of the rays of light from each reflector will be substantially the same. The broken lines in Fig. 3 indicate the propagation of the polarized light through the sheet of glass.

lAlthough alsingle large polarizing surface may be used if desired, a series of relatively small polarizing units 25 are preferably employed since with such an arrangement the system is much more compact and more ecient because of the shorter distance required for thev light to travel before reaching the glass sheet. Moreover, the use of a plurality of relatively small polarizing units providescheaper cost than a single unit of sui'licient size to give the required area of polarized light.' Also, ease of maintenance and a better cooling condition in dissipating the heat generated by the source of illumination.

More specifically, and upon reference to Fig. 9, it will be seen. that the source of illumination 26 for each polarizing unit 25 comprises a reflector 28 containingbne or more incandescent lamps 29, depending upon the width of the band of polarized light desired. The reflector 28 may be carried by a plurality of spaced. brackets 30 secured to an angle iro'n 3l suitablS7 supported at each end. The polarizing reflector 21 preferably consists of a sheet or slab of black glass which is practically opaque and provided with a polished surface so that it forms a good reflector. The reflector is placed at such an angle that the light from the lamps 29 will be polarized, the polarized rays belngreected upwardly through the glass sheet and analyzer unit as explained above. The polarizing reflector 21 may be supported at its inner edge Iupon a horizontal wooden strip 32 and adjacent its outer end by a horizontal angle member 33.

To accomplish the transverse inspection, the polarizing reflectors 21 extend longitudinally of the glass sheet and are arranged side by side transversely thereof and relative to one another as shown in Fig. 4, with the areas of light formed upon the glass by' the said reflectors being lndcated by the broken lines in Fig. 5. The areas of light so formed cooperate to produce the band ofpolarized light A. On the other hand, the polarizing units of the light polarizing means D are adapted to be arranged to eect the diagonal inspection of the glass and to this end the reectors 34 thereof extendv IobliquelyA beneath the sheet and are arranged side by sidetr'ansversely thereof as shown in Figs. 6 and '7. Thus, the arrangement of the reflectors is such that they form the band of polarized light B extending transversely of the sheet, while the vibrations of the polarized light extend at an angle of forty-five degrees with respect to the glass travel.

To obtain the above result, the polarizing reflectors 34 are tilted both laterally and longitudinally. More specifically, ea'ch reflector is tilted slightly about its longitudinal axis so that the longitudinal edge 35 thereof will be slightly above the opposite edge 3B. The reflector is further tipped about its transverse axis to'brng the end edge 31 thereof slightly higher than the opposite end edge 38. The angle of lateral inclination decreases from the reflector`c to the reflector d, while at the same time the'longitudinal inclination increases from reflector c to reector d. When the reflectors are arranged beneath the glass sheet in this manner, the areas of light formed thereby upon the glass will be as shown by the broken lines in Fig. 8, and which areas of light cooperate to form the. band of polarized sheet to the analyzers will vary in color v(when unit consisting of the pair of analyzers 23 and 2,4

carried by a substantially rectangular supporting plate 39 provided at its opposite ends with trunnions i0 and (it loosely received within the legs l2 and tt respectively of the substantially U- shaped supporting bracket dit which may be suitably mounted above and to onevside of the path of travel of the sheet upon the horizontal supporting member 2i. It is preferred that two analyzers Z3 and 2d be employed so that the inspector may simultaneously observe with both eyes the bands of polarized light A and B, each analyzer being set to receive the light from one of the light polarizing means. plate 39 can be rocked upon the trunnions il@ and i9 to move the analyzers into diierent positions to facilitate .the inspection of the glass. Threaded upon the outer end of trunnion ti is a nger piece @it and interposed between the said nger piece and leg J3 of bracket lit isa lcompression spring it which serves to maintain the plate t@ and likewise the analyzers 23 and 2t in adjusted position.

The analyzers 23 and 2li are 'of the ordinary type carrying a Nicol prism lconsisting of the two crystals il and it supported in a rotatable sleeve it so that the prism may be" adjustedr about its axis e. The sleeve d@ carries at one end thereof an eye piece 5@ and at its opposite end a mica quarter-wave or selenite plate 5i which, while preferably used, is not absolutely essential.

The analyzer 23 is stationarily mounted upon the supporting plate 35i while the analyzer 2Q' is The supporting using the quarter-wave or selenite plate) and intensity, depending upon the conditions of strain, ream, and other defects in the glass, and the colors and/or intensities as observed through the analyzers at different points across the sheet will indicate the condition of the glass with respect to strain, ream,"'etc., and any variation in these conditions is readily observed through the analyzers.

As brought out above, the defects present in sheet glass do not always extend in the samedirection and through actual experiment, it has been determined that streaks or bands of ream or unhomogeneity in sheet glass are most easily observed when they extend at an angle of fortyfive degrees with or lateral to the vibrations of polarized light. I have 'discovered that when a glass sheet is rotated about its axis parallel Cthe propagation of the polarized light and through. an'ang'le of 22%, degrees either side of the aforementioned angle of 45 degrees, the defects in the glass are still suciently visible for Vpractical inspection. Therefore, when inspecting"y a continuous strip of moving glass, with the vibrations of polarized light extending parallel to the glass `travel (such as vin eifecting the transverse indegrees at either side of a line extendingfat an movable toward and away from analyzer 23 tof t the observers eyes. Thus, the rotatable sleeve i9 of analyzer 2d may be rotatably mounted in a substantially square block 52 slidably receivedwithin a horizontal guideway 53 in supporting plate tit. The analyzer can be secured inadjusted position by means of a setscrew 5t passing through a slot 55 and received within block 52. This screw, however, is such that it will not interfere with the rotation of the analyzer about its axis e.

As is well understood, in the case of polarized light, the vibrations are all in one plane which4 is transverse to the direction of the rays. Therefore, before the polarized light passes through the glass sheet I6, it vibrates in only a single predetermined plane. On the other hand, the

analyzing Nicols are adjusted to pass light which the analyzers. In other words, any defects which are present in the glass sheet will cause a refraction of the rays of polarized light, resulting l in their vibration in a plane approaching right i? l. The rays of iight passing .through the giss angle of 45 degrees across the sheet in either dlrection. That is tosay, during the transverse inspection, the inspector, observing the glass through analyzer 223, willbe able to observe all defects extending within the includedy angle of the darkened areas or, otherwise stated, 221/2 degrees at either side of the diagonal linesf and g. On the other hand, with the vibrations of polarizedlight extending at an angle of forty-five degrees with respect to the glass travel (such as in eiecting the diagonal inspection of the glass), the zones of observation or, in other words, the areas of the lglass covered by the other analyzer 2d will be as shown by the darkened areas in Fig. 14. Thus, the areas visibleior inspection will extend 221/2 degrees at either side of a line drawn transversely across the sheet and also 227%/2 able to observe all defects within the darkened 'fr Sti areas extending 221/2 degrees at either side of the transverse line h and longitudinal line i. From the above, it will be readily apparent that when the darkened areas of the band of light A in Fig. 13 are superimposed over-the darkened areas of the band of light B in Fig'.14, the entire area of the glass sheet transversely thereof will be covered by the combined diagonal and transverse inspections. Hence, `by both transverse' and diagonal inspection, an inspector observing the glass through the analyzers 23 and i able to observe y-all defects transversely of the sheet.- Furthe'rmore, by setting the analyzers. 23 and 2l, sothat one analyzer will analyze the light from each light polarizing means, a single inspector can effect both the transverse and diagonal inspections simultaneously and without moving about their axes e. The result obtained is that tending in any direction across the glass.

a single inspector can readily and conveniently observe any unhomogeneity or other defects ex- That is to say, one of the analyzers 23 or 24 is set to transmit light from one of the polarizing means C or D, while the other analyzer is set to transmit light from the other polarizing means, so that an operator can observe the two bands of polarized light A and B simultaneously and thereby detect defects extending in any direction across the entire width of the sheet. 'I'his inspection can v and that various changes in the shape, size and arrangement of parts may be resorted to without departing from the spirit-oi the invention or the scope of the subjoined claims.

I claim: 1. In an inspection apparatusfo-r sheet glass, the combination of means for supporting the sheet and carrying it forwardly, light polarizing means arranged at one side of the supporting means for directing polarized light through the sheet to form a band of polarized light extending across said sheet, `with the vibrations of said" polarized light extending substantially at an angle o f 45 degrees with respect to the glass travel, separate ylight polarizing means also arranged at the same side of the supporting means for ydirecting polarized light through the sheet to form a secondhand of .polarized light extending A transversely thereof, with the vibrations of said second bandI of polarized light extending parallel to the glass travel, said first and second mentioned light polarizing means being so arranged relative to one another to superimpose the bands of polarized light formed thereby one upon the other, and an analyzer unit arranged at the opposite side of the sheet supporting means and comprisingl two analyzers adapted to transmit light polarizedv in different planes and mounted in such spaced relation as to permit the same to be used simultaneously by a single inspector, one of said analyzers being set to transmit light from said first lightI polarizing means while the fother analyzer is set to transmitlight' from said second light polarizing means so that the operator can observe the two superimposed bands of polarized light simultaneously and thereby detect defects extending in any directionacross the entire Width of the sheet.

2. In an inspection apparatus for sheet glass, the combination of means for supporting the sheet and carrying it forwardly, light polarizing means arranged at one side of the supporting means and including a plurality of polarizing units arranged side by side,veach unit comprising a source of illumination and an inclined polarizing reiiector-arranged in opposition to the source of illumination in position to receive the light therefrom and refiect the polarized portion thereof through the glass sheet, the reflectors of the several polarizing units being so arranged with respect to one another and relative to the supporting means to form a band of polarized light extending across said sheet, with the vibrations of said polarized light extending substantially at an angle of 45 degrees with respect to the glass travel, separate light polarizing means arranged at the same side of the supporting means and also including a plurality of polarizing units arranged side by side, each comprising a source of illumination and an inclined polarizing reflector" arranged in opposition to the source of illumination in position to receive the light therefrom and reflect the polarized portion thereof through the glass sheet, the reectors oiathe several last-mentioned polarizing units being so arranged with respect to one another and relative to the supporting means to form a second band of polarized light extending transversely of said sheet, with th'e vibrations of said second band of polarized light extending parallel to the glass travel, said iirst and second mentioned light polarizing means being so arranged relative to one another to superimpose the bands of polarized light formed thereby one upon the other, and an analyzer unit arranged at the opposite side ofthe sheet supporting means and comprising two analyzers adapted to transmit light polarized in diierent planes and mounted in such spaced relation as to permit the same to be used simultaneously by a single inspector, one of said analyzers being set to transmit light from said first light polarizing means while the other analyzer is set to transmit light 'from said second light polarizing means so that the operator can observe the two superimposed bands of polarized light simultaneously` EM'MIE'I'I L. WALTERS. 

